Preparation Of Supported-ionic Liquids And Their Catalytic Performance In Organic Synthesis

Supported-ionic liquids have attracted growing research interest due to the environmentally benign and economic advantages, such as the reducing usage of ionic liquids, possible application in a continuous reactor and the easier separation of the catalyst from the reaction media, allowing the recovery of the solid catalyst and eventually its reuse. Furthermore, the designability of the ionic liquids gives us more chances to manipulate the structures of them to achieve ionic liquids of special properties according to the given reactions. In this paper, fourteen of ionic liquids and eleven of supported-ionic liquids were synthesized and used as catalysts for the synthesis ofβ-enaminones and the esterification under smooth reaction conditions. Effect of the catalyst structure on their catalytic activity was also investigated.The synthesis ofβ-enaminone from aniline and acetyl acetone over eleven of imidazolium ionic liquids and eleven of supported-ionic liquids was investigated. The results showed that: when the anions remain unchanged, the order of the catalytic performance of the imidazolium ionic liquids is:[hmim]+> [bmim]+>[bmmim]+. With a same cation of 1-n-butyl-3-methylmidazolium, the ionic liquids with different anions were used for the condensation reaction under the same reaction conditions and exhibited an activity order of Br-> PF6-> BF4-, I-> Cl-> H2PO4-, HSO4-. In spite of the reducing usage of ionic liquids, immobilized ionic liquid catalysts presented obviously improved activity. The catalytic activity order of the cation is [bmim]+> [hmim]+> [bmmim]+, and the activity order of the anion is PF6-, BF4-> Br-> I-> Cl-> H2PO4-, HSO4-. Among all the catalysts tested, [bmim]BF4/silica and [bmim]PF6/silica proven to be the most efficient since the reaction could be carried out in excellent yield,93.6 and 92.2%, respectively, at room temperature. Furthermore, [bmim]BF4/silica was conveniently separated form the products and reused five times without considerable loss of activity.The reaction of benzyl alcohol with acetic anhydride over six of supported-ionic liquids were investigated. The results showed that [bmim]HSO4/silica and [bmim]H2PO4/silica were the most efficient since there are the H within the anion, which have stronger acidity. The reaction could be carried out in excellent yield, of 89.9 and 96.2%, respectively, at room temperature. However, these catalysts can not be reused, so we design the ionic Liquids [MIMPS]HSO4 and [TEAPS]HS04, which be modified with PS. The product ester can be easily separated from the system, thus promoting the reaction. The [TEAPS]HSO4 has a good catalytic activity, the reaction could be carried out in 96% yield in 1h. Furthermore, the catalyst has good stability and was reused four times without significantly decreased of activity. At the same time, the catalytic performance of these ionic liquid catalysts for the Fischer esterification reaction was also carried out. compared with traditional acid catalyst of H3PW12O40, the [TEAPS]HSO4 as a a phase transfer catalyst can catalyzed Fischer esterification reaction under the conditions of toluene-free, lower temperature, shorter reaction time, easier operation, exhibiting environmentally benign and economic advantages.